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Noise is a pollutant that is controllable and is amenable to abatement technology. Standards have been set out by the Environmental Protection Agency which sets the standards for allowable noise levels for the human ear. Noise intensity is measured in decibels and the scale by which it is measured is logarithmic. This means that a 10 decibel increase in noise constitutes a doubling of loudness.
Distance also reduces the noise reaching the ear the further a person is away from the source of noise. Noises above 45 decibels will disturb a person’s sleep, while noises above 120 decibels can become painful and cause hearing damage. Besides hearing damage, noise can also affect persons in other ways that would need them to seek medical attention. Sound level meters measure the pressure levels caused by the sound and translate them into electrical impulses that are registered on a meter. Digital sound level meters can measure noises in the range of 40 to 130 decibels with an accuracy of ~+mn~2 decibels.
Image: Extech.com - 407730 LCD Digital Sound Level Meter
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Causes of Urban Noise Pollution
Noise pollution is caused by people or machines that produce a high environmental noise that has a deleterious effect on the health of humans and animals. Vehicles and engines like generators, compressors, and drilling machines are the chief causes of noise pollution in urban areas. The noise levels are further accentuated by the reflecting surfaces of buildings and glass which can amplify these noises till they reach unbearable levels.
The rhythmic nature of the noise created by these urban machines, or by audio systems used for entertainment, causes constant irritation to the ear. City planners have set standards for allowable noise and also have laws in place which allow such equipment only at particular times. Noise abatement methods using sound baffles or absorbers are nowadays standard fitments in buildings and on urban roads. Manufacturers of transportation and other equipment have also addressed the matter of urban noise pollution by introducing sound absorbing techniques around their engines.
Image: Wikipedia - Jackhammer
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Impacts of Noise Pollution
Noise is one of the leading causes of hearing impairment that afflicts a substantial portion of the human population especially around urban centers. Such impairment is permanent and is now even occurring at very young ages due to the proliferation of audio systems and their constant use by the younger generation.
Health effects are noticed once noise levels cross 85 decibels and exposure to the noise is for a prolonged length of time. Loudness of noise doubles with every 10 decibel increase in noise levels and damage to hearing can be caused by even very short exposure to it. The damage to hearing is caused by the noise affecting the hair cells in the inner ear which are very delicate and can get irretrievably damaged.
Damage to hearing can be reduced with the use of ear plugs or ear muffs and their use is now recommended for most industrial workers exposed to constant noise. Turning down the volume of audio equipment and reducing the time spent in noisy environments can also help to reduce hearing damage.
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Effects of Noise Pollution on Animals
Auditory effects of noise on animals are the same as in humans and can involve hearing loss and a reduced sensitivity to noise. This affects the animals functioning abilities and can cause their hunting faculties to be reduced.
Noise causes stress. This in turn can produce hormonal changes in animals that affect their fight or flight responses. They will have reactions that are not appropriate, and this can affect their energy resources which in turn can make them more susceptible to predators or disease.
Noise can also disrupt behavioral patterns in animals and may force them to change their habitats which will then directly impinge on their survival in conditions that they are unused to.
Noise can affect those animals the most which are dependent on their auditory senses for their survival. It could also affect their abilities to communicate and thus their mating activities.
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